# Measuring instruments: Micrometre screw gauge vs vernier caliper

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## Measuring instruments: Micrometre screw gauge vs vernier calliper

### What is measurement?

This is the bedrock of the trade and statistics used for centuries now. It is the ability of one to ascertain the height, size and quantity of something by comparison.

Measurement is defined as the determination of the quantity, size or magnitude of an object or substance by comparing it with something of known or standard measurement.

### Scale

This is an indicator of the different units of measurement. All measuring devices must  come with a type scales using units of metric systems.

Note: Length, mass and time are three standard units. Other units includes:
Candelas (Cd): For measurement of intensity.

Mole (m): For measurement of substances with respect to atom.

Kelvin (k): For measurement of temperature.

### Micrometre screw gauge.

This is a measurement instrument used for measuring small distances of objects that are too small for direct measurement of diameters greater than 2.5cm that can fit within the jaws of the micrometre screw gauge as seen below;

Uses: For measuring diameter of meter wire, thickness of glass plate, for small spherical objects etc.

How to read a Micrometer Screw Gauge

 A clarification of where the Main scale and thimble scale is.
 Different micrometer screw gauge comes with different units of measurements. From the figure the Main scale(mm) reads 5.5mm, as that is where the mark ends. Then the Thimble scale(mm) reads 0.3mm, which is the point the thimble scale lines up with the main scale.

Write your answers the the comment section for the practice questions below.

### Vernier caliper

This is a measuring instrument similar to hygrometer screw gauge but are quite different. The vernier callipers are used for measurement of internal and external distances allowing larger scales than the micrometre screw gauge.

 Vernier Caliper
For the figure above,

1. Outside jaws
2. Inside jaws
3. Depth probe
4. Main scale (Lower)
5. Main scale (upper)
6. Minor scale (Lower)
7. Minor scale (upper)
8. Retainer (used to block movable parts)

Uses: this instrument is used for measurement of cylinders and hollow tubes (e.g. test tubes).

How to read a Vernier Caliper

Note: When the vernier calliper is shut (that is; not measuring anything), the major and minor axis line up.

To measure, you'll need to put the object desired between the Jaws of the measuring scale and close it.

For Example:

From the figure below, the zero (0) on the minor scale is a bit past an exact line up with the major axis, it is a little past the 0.7cm mark on the major axis.

For the minor scale (lower) reading:
Since the zero (0) on the minor scale does not line up well with the major scale exactly, we need to find where on the entire minor scale it does.
From the figure above, the 7th mark on the minor scale lines up perfectly with the major scale.

For the smallest unit of measurement:
At the tail of the vernier caliper, you'll find a number (in this case it's 0.05mm), which is the unit difference for the minor scale. So the minor scale lines up at a 0.7mm
 Tail of the vernier caliper

Final Calculations

Reading of Vernier Caliper = 0.7cm + 0.7mm
= 0.7cm + 0.07cm
= 0.77cm (plus or minus 0.005cm)

#### Conclusion

This instrument are quite easy to use and remember to use them for measuring the right objects.
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